1. Field of the Invention
The present invention relates to an aircraft, missile, projectile, or underwater vehicle with an improved control system, an improved control system and a method of maneuvering an aircraft, missile, projectile, or underwater vehicle. More particularly, the present invention relates to an aircraft, missile, projectile, or underwater vehicle with control surfaces that are movable along a track. The present invention further relates to a method of controlling an aircraft, missile, projectile, or underwater vehicle using such a control system.
2. Technical Background
The ability to adaptively modify and control a vehicle's static and dynamic stability in-flight has vast potential in a diverse array of aeronautical and underwater applications, including extreme vehicle maneuvering, collision avoidance, collision seeking, end-game maneuvering, stall prevention, and managing aerodynamic forces and moments. There is no doubt that in the era of growing aeronautical and aerospace use, air vehicles with fast-acting control surfaces and methodologies that allow dynamic, in-flight reconfiguration of the vehicle's stability and aerodynamic performance are critical to the success and development of next-generation, high-performance vehicles. Examples include weapons that are designed to seek and destroy moving and emerging high-priority targets, active flares that are deployed from aircraft to defend against enemy missiles, or fighter aircraft that need rapid maneuvering capabilities during dog-fighting. In general, it is highly desirable to have an aircraft, missile, projectile, or underwater vehicle be able to readjust its path in a quick and effective manner. In the case of missiles or projectiles, it is not only desirable but necessary to possess the ability to actively adjust vehicle stability and maneuverability in-flight so as to sustain high loads during launch and to pursue moving targets, respectively.
Stability and maneuverability are functions of the relative positions of center of gravity and center of pressure. The center of pressure is determined by the relative placement of surface area. As the fluid flows over the surface, it exerts pressure upon that surface. By integrating the total pressure around the vehicle, the net force and moment is determined, which defines the vehicle's stability. With more pressure towards the rear of the vehicle, the center of pressure moves towards the rear, and vice versa. The vehicle's center of gravity is based upon the weight distribution, in that more weight towards the front or the back of the vehicle will correspondingly alter the center of gravity towards the front or back, respectively. The further the center of pressure is located aft of the center of gravity, the greater the stability provided to the vehicle. Alternatively, reducing the distance between the center of mass and the center of pressure leads to a less stable, and hence, a more maneuverable vehicle. Consequently, to create a more stable vehicle, control surfaces are typically placed near the rear, behind the center of gravity. This increase in stability, however, has the drawback of leading to a less maneuverable configuration.
The trade-off between stability and maneuverability is always a challenging assessment in the case of vehicles that require both “stable flight” and “supermaneuverability” during different stages of their flight envelope. An example of such a vehicle is a small rocket-powered flare or a projectile that is used as a defensive countermeasure for aircraft against enemy missiles. For a successful employment of such a countermeasure system, the flare needs to be fired from an aircraft in such a way that it can be maneuvered into the path of the incoming missile for physical interception and destruction. This style of execution requires both heightened stability and supermaneuverability, which is uncharacteristic of traditional flares or air vehicles.
Additional problems with control surface designs arise when a missile or projectile must be fired at an angle from a fast-moving aircraft. A missile or projectile fired at an angle from a quickly moving aircraft must be extremely stable to overcome the high crosswinds and yawing moment during the launch phase. Inadequate stability will result in the missile or projectile tumbling out of control shortly after launch. Air-to-air and air-to-ground missiles are normally fired in the same direction of the aircraft from which they are launched. Any change in direction away from that of the aircraft from which the missile or projectile is fired occurs after the missile or projectile is in flight. This eliminates any crosswinds caused by the forward motion of the aircraft as the winds will be parallel with the bodies of the aircraft and missile or projectile. However, when an air-to-air or air-to-ground missile is fired at any angle not directly forward or directly backward of the aircraft (0 and 180 degrees, respectively), it is subject to crosswinds generated by the forward movement of the aircraft. The higher the launch angle is away from 0 or 180 degrees, the greater the crosswinds. The crosswinds will increase approaching 90 degrees from forward where they will be greatest, and decrease approaching 180 degrees where they will return to 0. Overcoming the crosswinds and yawing moment requires large control surfaces for stability. But a missile or projectile with large control surfaces will not be able to adequately maneuver because its large control surfaces place its center of pressure far behind its center of mass. This problem has thus far prevented large-scale use of aircraft-launched missiles or projectiles that are launched at an angle.
The stability-for-maneuverability trade-off is worthwhile in the case of long-range missiles and other types of projectiles that require stability, and with conventional fixed-wing aircraft, such as commercial aircraft, that do not conduct complex maneuvers. The maneuverability-for-stability trade-off is worthwhile for missiles and projectiles that require great maneuverability and are not intended to fly long distances at straight trajectories and for aircraft, such as fighter planes, that must perform complex maneuvers. However, a problem arises when both traits of maneuverability and stability must be combined over the flight of an aircraft, missile, projectile, or underwater vehicle.
Normally, stability and maneuverability are not required during the same time period but rather at different segments of a flight. An example of a missile requiring both stability and maneuverability at separate segments of a flight is a destructive expendable (DEX). A DEX is a small missile used as a defensive measure against a surface-to-air missile or air-to-air missile fired at an aircraft. A DEX is fired from an aircraft when an incoming missile is detected. Because the incoming missile can approach the aircraft from any angle (upper/lower/front/rear hemispheres), the DEX must be able to be launched at any angle, not just forwards or backwards. The DEX then flies towards the incoming missile and intercepts it, thus destroying the threat to the aircraft. Both firing from the aircraft and flight towards the missile require heightened stability provided by large aftward control surfaces. However, when acquiring the target and approaching the incoming missile, the DEX requires maneuverability for intercepting the missile.
Creating vehicles with high stability and maneuverability has long been a goal in the art, and has been accomplished by a number of means. Canards, elevators, ailerons, elevons and other forms of control surfaces are typically used to provide control and stability. However, most vehicles have a single-point design, where the design of the aerodynamic control system is optimized for the conditions likely to be encountered for the majority of the vehicle's flight path. To design vehicles that are both stable as well as maneuverable, multi-point designs involving adaptive, in-flight modifications to the control surfaces are proposed.
Moveable control surfaces have also been developed to increase the maneuverability of missiles, aircraft or projectiles. These control surfaces control the direction of the aircraft, missile, projectile, or underwater vehicle by redirecting airflow over the body and control surfaces during flight. The moveable control surfaces either rotate about their connection point to the body, or the control surfaces' trailing edges are moved upwards and downwards such as ailerons or rudders. Moveable control surfaces, however, do not address the problem of the aftward center of pressure created by large control surfaces placed towards the rear of the aircraft, missile, projectile, or underwater vehicle. Moveable control surfaces also provide no additional stability for a missile or projectile when launched at an angle from a moving aircraft because moveable control surfaces cannot redirect any crosswinds traveling perpendicular to the missile.
Additionally, control systems of the moveable control surfaces add more weight and complexity, thus counteracting some of the maneuverability gained from the moveable control surfaces.
In view of the foregoing inherent disadvantages with presently available aircraft, missile, projectile, or underwater vehicle control devices, it an object of the present invention to develop a system for controlling aircraft, missiles, projectiles or underwater vehicles that allows for these devices to be successfully maneuvered. In the case of a missile or projectile to be launched at an angle from a moving aircraft, such a system should allow it to maintain a stable flight to its target or to perform rapid maneuvers in order to intercept and destroy its target. Additionally, there is a need to develop a method for effectively controlling these aircraft, missiles, projectiles or underwater vehicles in order to enhance their mission.